U.S. patent number 6,503,330 [Application Number 09/470,279] was granted by the patent office on 2003-01-07 for apparatus and method to achieve continuous interface and ultrathin film during atomic layer deposition.
This patent grant is currently assigned to Genus, Inc.. Invention is credited to Carl Galewski, Thomas E. Seidel, Ofer Sneh.
United States Patent |
6,503,330 |
Sneh , et al. |
January 7, 2003 |
Apparatus and method to achieve continuous interface and ultrathin
film during atomic layer deposition
Abstract
A method and apparatus for performing atomic layer deposition in
which a surface of a substrate is pretreated to make the surface of
the substrate reactive for performing atomic layer deposition.
Inventors: |
Sneh; Ofer (Mountain View,
CA), Seidel; Thomas E. (Sunnyvale, CA), Galewski;
Carl (Aromas, CA) |
Assignee: |
Genus, Inc. (Sunnyvale,
CA)
|
Family
ID: |
23866961 |
Appl.
No.: |
09/470,279 |
Filed: |
December 22, 1999 |
Current U.S.
Class: |
118/715;
118/723ER; 118/723IR; 118/723ME |
Current CPC
Class: |
C23C
16/02 (20130101); C23C 16/0272 (20130101); C23C
16/45536 (20130101); C23C 16/45544 (20130101) |
Current International
Class: |
C23C
16/02 (20060101); C23C 16/455 (20060101); C23C
16/44 (20060101); C23C 016/00 () |
Field of
Search: |
;118/715,723ME,723IR,723ER |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 442 490 |
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Aug 1991 |
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EP |
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0 442 490 |
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May 1995 |
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EP |
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0 511 264 |
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Aug 1995 |
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EP |
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60-10625 |
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Jan 1985 |
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JP |
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2-152251 |
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Jun 1990 |
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JP |
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5-152215 |
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Jun 1993 |
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JP |
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8-236459 |
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Sep 1996 |
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JP |
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10-102256 |
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Apr 1998 |
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JP |
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WO-91/10510 |
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Jul 1991 |
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WO |
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|
Primary Examiner: Lund; Jeffrie R.
Attorney, Agent or Firm: Blakely Sokoloff Taylor &
Zafman LLP
Government Interests
The United States Government has rights in this invention pursuant
to Contract No. F33615-99-C-2961 between Genus, Inc. and the U.S.
Air Force Research Laboratory.
Claims
We claim:
1. An apparatus comprising: a mixing manifold having a common
carrier gas inlet and a split flow of carrier gas after the carrier
gas inlet, said mixing manifold having a first chemical inlet to
introduce a first precursor chemical in one flow path of the split
flow of the carrier gas and having a second chemical inlet to
introduce a second precursor chemical in a second flow path of the
split flow of the carrier gas; a reactor coupled to said mixing
manifold to receive the first precursor chemical during a first
time period and the second precursor chemical during a second time
period to perform atomic layer deposition.
2. The apparatus of claim 1 wherein the carrier gas flows at a
constant regulated flow to said reactor.
3. The apparatus of claim 1 wherein the carrier gas flows at a
constant regulated flow to introduce the first precursor chemical
into said reactor during the first time period and to purge the
first precursor chemical from said reactor after the first time
period, but prior to the second time period.
4. The apparatus of claim 3 wherein the carrier gas introduces the
second precursor chemical into said reactor during the second time
period and to purge the second precursor chemical from said reactor
after the second time period.
5. The apparatus of claim 1 further including a plasma source
coupled to said mixing manifold and said reactor to introduce
plasma into said reactor.
6. The apparatus of claim 1 further including a plasma source
coupled between said mixing manifold and said reactor to vertically
introduce the first and second precursor chemicals and plasma into
said reactor.
7. The apparatus of claim 1 further including a gas distributor
disposed on said reactor to distribute the carrier gas entering
said reactor.
8. The apparatus of claim 1 further including a downstream vacuum
pump and throttle valve to regulate the carrier gas to have a
constant regulated flow.
9. An apparatus comprising: a mixing manifold having a common
carrier gas inlet and a split flow of carrier gas after the carrier
gas inlet, said mixing manifold having a first chemical inlet to
introduce a first precursor chemical into a first flow path of the
split flow of the carrier gas and having a second chemical inlet to
introduce a second precursor chemical into a second flow path of
the split flow of the carrier gas, the carrier gas having a
constant regulated flow; a reactor coupled to said mixing manifold
to receive the first precursor chemical during a first time period
and the second precursor chemical during a second time period to
perform atomic layer deposition to deposit a film layer on a
wafer.
10. The apparatus of claim 9 wherein the carrier gas purges the
first precursor chemical from said reactor after the first time
period, but prior to the second time period.
11. The apparatus of claim 10 wherein the carrier gas purges the
second precursor chemical from said reactor after the second time
period.
12. The apparatus of claim 11 further including a plasma source
coupled to said mixing manifold and said reactor to introduce
plasma into said reactor.
13. The apparatus of claim 11 further including a plasma source
coupled between said mixing manifold and said reactor to vertically
introduce the first and second precursor chemicals and plasma into
said reactor.
14. The apparatus of claim 11 further including a gas distributor
disposed on said reactor to distribute the carrier gas entering
said reactor.
15. The apparatus of claim 10 further including a downstream vacuum
pump and throttle valve to regulate the carrier gas to have the
constant regulated flow.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to semiconductor technology
and, more particularly, to a method and apparatus for the practice
of atomic layer deposition.
2. Background of the Related Art
In the manufacture of integrated circuits, many methods are known
for depositing and forming various layers on a substrate. Chemical
vapor deposition (CVD) and its variant processes are utilized to
deposit thin films of uniform and, often times conformal coatings
over high-aspect and uneven features present on a wafer. However,
as device geometries shrink and component densities increase on a
wafer, new processes are needed to deposit ultrathin film layers on
a wafer. The standard CVD techniques have difficulty meeting the
uniformity and conformity requirements for much thinner films.
One variant of CVD to deposit thinner layers is a process known as
atomic layer deposition (ALD). ALD has its roots originally in
atomic layer epitaxy, which is described in U.S. Pat. Nos.
4,058,430 and 4,413,022 and in an article titled "Atomic Layer
Epitaxy" by Goodman et al.; J. Appl. Phys. 60(3), Aug. 1, 1986; pp.
R65-R80. Generally, ALD is a process wherein conventional CVD
processes are divided into single-monolayer depositions, wherein
each separate deposition step theoretically reaches saturation at a
single molecular or atomic monolayer thickness or less and, then,
self-terminates.
The deposition is an outcome of chemical reactions between reactive
molecular precursors and the substrate (either the base substrate
or layers formed on the base substrate). The elements comprising
the film are delivered as molecular precursors. The desired net
reaction is to deposit a pure film and eliminate "extra" atoms
(molecules) that comprise the molecular precursors (ligands). In a
standard CVD process, the precursors are fed simultaneously into
the reactor. In an ALD process, the precursors are introduced into
the reactor separately, typically by alternating the flow, so that
only one precursor at a time is introduced into the reactor. For
example, the first precursor could be a metal precursor containing
a metal element M, which is bonded to an atomic or molecular ligand
L to form a volatile molecule ML.sub.x. The metal precursor reacts
with the substrate to deposit a monolayer of the metal M with its
passivating ligand. The chamber is purged and, then, followed by an
introduction of a second precursor. The second precursor is
introduced to restore the surface reactivity towards the metal
precursor for depositing the next layer of metal. Thus, ALD allows
for single layer growth per cycle, so that much tighter thickness
controls can be exercised over standard CVD process. The tighter
controls allow for ultrathin films to be grown.
In practicing CVD, a nucleation step is assumed when a film of
stable material is deposited on a stable substrate. Nucleation is
an outcome of only partial bonding between the substrate and the
film being deposited. Molecular precursors of CVD processes attach
to the surface by a direct surface reaction with a reactive site or
by CVD reaction between the reactive ingredients on the surface. Of
the two, the CVD reaction between the reactive ingredients is more
prevalent, since the ingredients have much higher affinity for
attachment to each other. Only a small fraction of the initial film
growth is due to direct surface reaction.
An example of nucleation is illustrated in FIGS. 1-3. FIG. 1 shows
a substrate 10 having bonding locations 11 on a surface of the
substrate. Assuming that the CVD reaction involves a metal (M) and
a ligand (L.sub.x) reacting with a non-metal (A) and hydrogen
(H.sub.z), the adsorbed species diffuse on the surface and react
upon successful ML.sub.x -AH.sub.z collisions. However, the
reaction does not occur at all of the potential attachment (or
bonding) locations 11. Generally, defect sites (sites having
irregular topology or impurity) are likely to trap molecular
precursors for extended times and, therefore, have higher
probability to initiate nucleation. In any event, as shown in FIG.
1, the bonding of the precursor to the surface occurs at only some
of the bonding locations 12.
Subsequently, as shown in FIG. 2, the initial bonding sites 12
commence to further grow the thin film material on the surface of
the substrate 10. The initial reaction products on the surface are
the nucleation seed, since the attached products are immobile and
diffusing molecular precursors have a high probability to collide
with them and react. The process results in the growing of islands
13 on the substrate surface together with the continuous process of
creating new nucleation sites 14. However, as the islands 13 grow
larger, the formation of new nucleation seeds is suppressed because
most of the collisions occur at the large boundaries of the islands
13.
As the islands 13 enlarge three-dimensionally, most of the
adsorption and reaction processes occur on the island surfaces,
especially along the upper surface area of the islands 13.
Eventually, this vertical growth results in the islands becoming
grains. When the grains finally coalesce into a continuous film,
the thickness could be on the order of 50 angstroms. However, as
shown in FIG. 3, the separated nucleation sites can result in the
formation of grain boundaries and voids 15 along the surface of the
substrate, where potential bonding sites failed to effect a bond
with the precursor(s). The grain boundaries and voids 15 leave
bonding gaps along the surface of the substrate so that substantial
film height will need to be reached before a continuous upper
surface of the film layer is formed.
Although the results described above from nucleation is a problem
with the standard CVD process, the effect is amplified with ALD.
Since ALD utilizes one precursor at a time, the initial bonding
will occur due to surface reaction of the initial precursor with
sparse surface defects. Accordingly, seed nucleation sites 12 are
very sparse (more sparse than CVD) and nucleation proceeds by
growing ALD layers on these few seed sites. As a result, the nuclei
grow three-dimensional islands 13 and coalesce only at thickness
that are comparable to the distance between the nucleation seeds.
That is, the voids 15 could be much larger in size, so that a much
higher structure is needed to provide a continues upper surface for
the film when only ALD is used.
Accordingly, if an ALD film can initiate growth on a substrate
predominantly by nucleation, the film grows discontinuously for a
much thicker distance. Ultimately a much thicker film is
practically needed in the case of ALD to achieve continuous film,
than that which can be obtained from CVD processes.
The present invention is directed to providing a technique to
deposit ALD thin films of reduced thickness that has continuous
interface and film.
SUMMARY OF THE INVENTION
A method and apparatus for performing atomic layer deposition in
which a surface of a substrate is pretreated to make the surface of
the substrate reactive for performing atomic layer deposition
(ALD). As a result, the ALD process can start continuously without
nucleation or incubation, so that continuous interfaces and
ultrathin films are formed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional diagram showing a problem encountered
with prior art CVD processes, in which sparse seed nuclei are
formed to initiate film growth by non-continuous nucleation.
FIG. 2 is a cross-sectional diagram showing the start of nucleation
emanating from the chemical attachment shown in FIG. 1, in which
the spacing between the nucleation sites results in the formation
of separated islands as the deposition process progresses.
FIG. 3 is a cross-sectional diagram showing the result of further
growth of the deposited layer of FIG. 2, in which the formation of
grain boundaries and voids requires more than desirable thickness
to be deposited to obtain a continuous layer at the surface.
FIG. 4 is a cross-sectional diagram showing an embodiment of the
present invention in pretreating a surface of a substrate to
activate the surface, prior to performing atomic layer deposition
to grow an ultra thin film layer.
FIG. 5 is a cross-sectional diagram showing the presence of many
more active sites on the surface of the substrate after surface
pretreatment shown in FIG. 4 is performed.
FIG. 6 is a cross-sectional diagram showing a first sequence for
performing ALD when a first precursor is introduced to the prepared
surface of FIG. 5.
FIG. 7 is a cross-sectional diagram showing a formation of ligands
on the substrate surface of FIG. 6 after the first precursor reacts
with the pretreated surface and the subsequent introduction of a
second precursor.
FIG. 8 is a cross-sectional diagram showing the restoration of the
substrate surface of FIG. 7 so that the first precursor can be
reintroduced to repeat the ALD cycle for film growth and, in
addition, a continuous interface layer of the desired film is
deposited on the substrate by the sequences of FIGS. 5-7.
FIG. 9 is a cross-sectional diagram showing a formation of a next
ALD monolayer atop the first monolayer shown in FIG. 8 to further
grow the layer above the substrate one atomic/molecular layer at a
time.
FIG. 10 is a cross-sectional diagram showing an alternative
pretreatment technique in which an intermediate layer is formed to
provide activation sites on the surface of the substrate prior to
performing ALD.
FIG. 11 is a block diagram showing one reactor apparatus for
performing ALD, as well as pretreating the surface by practicing
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The practice of atomic layer deposition (ALD) to deposit a film
layer onto a substrate, such as a semiconductor wafer, requires
separately introducing molecular precursors into a processing
reactor. The ALD technique will deposit an ultrathin film layer
atop the substrate. The term substrate is used herein to indicate
either a base substrate or a material layer formed on a base
substrate, such as a silicon substrate. The growth of the ALD layer
follows the chemistries associated with chemical vapor deposition
(CVD), but the precursors are introduced separately.
In an example ALD process for practicing the present invention, the
first precursor introduced is a metal precursor comprising a metal
element M bonded to atomic or molecular ligand L to make a volatile
molecule ML.sub.x (the x, y and z subscripts are utilized herein to
denote integers 1, 2, 3, etc.). It is desirable that the ML.sub.x
molecule bond with a ligand attached to the surface of the
substrate. An example ligand is a hydrogen-containing ligand, such
as AH, where A is a nonmetal element bonded to hydrogen. Thus, the
desired reaction is noted as AH+ML.sub.x.fwdarw.AML.sub.y +HL,
where HL is the exchange reaction by-product.
However, in a typical situation as noted in the Background section
above, the substrate surface does not possess ample bonding sites
for all the potential locations on the surface. Accordingly, the
ML.sub.x precursor bonding to the surface can result in the
formation of islands and grains which are sufficiently far apart to
cause the problems noted above. In order to grow continuous
interfaces and films, the present invention is practiced to
pretreat the surface of the substrate prior to ALD in order to have
the surface more susceptible to ALD. In the preferred embodiment
the substrate surface is first treated to make the surface more
reactive. This is achieved by forming reactive termination on the
surface which will then react with the first ALD precursor.
FIG. 4 shows one embodiment for practicing the present invention.
In FIG. 4, a substrate 20 (again, substrate is used herein to refer
to either a base substrate or a material layer formed on a base
substrate) is shown upon which ALD is performed. Instead of
applying the ML.sub.x precursor initially onto the substrate 20,
one or more radical specie(s), including such species as oxygen,
hydrogen, OH, NH.sub.2, Cl and F, is introduced to react with a
surface 21 of the substrate 20. The species can be remote plasma
generated and carried to the processing chamber. The reactive
species can be selected to react with most surfaces, however, the
particular specie selected will depend on the surface chemistry. A
given specie is utilized to modify the surface 21. The reactive
specie typically will modify the surface by exchanging other
surface species and/or attaching to previously reconstructed
sites.
For example, SiO.sub.2 surface with approximately 100% siloxane
SiOSi bridge is generally inert. OH, H or O radical exposure can
efficiently insert HOH into the SiOSi to generate 2 Si--OH surface
species that are highly reactive with ML.sub.x molecular precursor.
In FIG. 4, a generic AH.sub.z reaction is shown to treat the
surface 21 of the substrate 20. A number of example reactions using
a particular species to treat various surfaces is described later
below.
The introduction of the pretreatment plasma into the processing
chamber containing the substrate 20 results in the formation of
surface species at various desired bonding sites. Thus, as shown in
FIG. 5, the surface is shown containing AH sites. It is desirable
to have the AH species at many of the potential bonding sites.
Subsequently, as shown in FIG. 6, the first precursor ML.sub.x is
introduced to start the ALD process for growing a film layer having
the composition MA.
It should be noted that the prior art practice of performing ALD
commences by the introduction of ML.sub.x. Since the prior art does
not pretreat the surface 21, there is a tendency for the surface to
have lot less potential bonding sites. That is, there are lot less
AH sites on non-treated surfaces versus the number available for
the pretreated surface 21 shown in FIG. 6. Accordingly, with less
bonding sites on the surface, the earlier described problems
associated with nucleation can occur. However, the pretreated
surface 21 allows for many more bonding sites to be present on the
surface to reduce the above-noted problem.
FIGS. 7-9 show the remaining sequence for performing ALD. After the
ML.sub.x precursor is introduced, the AH+ML.sub.x.fwdarw.AML.sub.y
+HL reaction occurs, wherein HL is exchanged as the reaction
by-product. As shown in FIG. 7, the surface of the substrate 21 now
contains the MA-L combination, which then reacts with the second
precursor comprising AH.sub.z. The second precursor, shown here
comprising a nonmetal element A and hydrogen reacts with the L
terminated sites on the surface 21. The hydrogen component is
typically represented by H.sub.2 O, NH.sub.3 or H.sub.2 S. The
reaction ML+AH.sub.z.fwdarw.MAH+HL results in the desired
additional element A being deposited as AH terminated sites and the
ligand L is eliminated as a volatile by-product HL. The surface 21
now has AH terminated sites, as shown in FIG. 8.
At this point of the process, the first precursor has been
introduced and deposited by ALD, followed by the second precursor,
also by ALD. The sequence of surface reactions restores the surface
21 to the initial condition prior to the ML.sub.x deposition,
thereby completing the ALD deposition cycle. Since each ALD
deposition step is self-saturating, each reaction only proceeds
until the surface sites are consumed. Therefore, ALD allows films
to be layered down in equal metered sequences that are identical in
chemical kinematics, deposition per cycle, composition and
thickness. Self-saturating surface reactions make ALD insensitive
to transport non-uniformity either from flow engineering or surface
topography, which is not the case with other CVD techniques. With
the other CVD techniques, non-uniform flux can result in different
completion time at different areas, resulting in non-uniformity or
non-conformity. ALD, due to its monolayer limiting reaction, can
provide improved uniformity and/or conformity over other CVD
techniques.
FIG. 9 illustrates the result of a subsequent ALD formation of the
MA layer when the next ML.sub.x sequence is performed to the
surface of the substrate shown in FIG. 8. Thus, additional ALD
deposition cycles will further grow the film layer 22 on the
surface 21, one atomic or molecular layer at a time, until a
desired thickness is reached. With the pretreatment of the surface
21, nucleation problems noted earlier are inhibited, due to ample
bonding sites on the surface. Thus, the initial ALD layers, as well
as subsequent ALD layers, will have ample bonding sites on the
surface to attach the reactive species. Continuous ultrathin film
layers of 50 angstroms and under can be deposited with acceptable
uniformity and conformity properties when practicing the present
invention.
It is appreciated that the pretreatment of the surface 21 can be
achieved to deposit enough radical species to exchange with the
surface. In this instance, these radical species (shown as AH in
the example illustrated) provide termination sites for bonding to
the ML.sub.x precursor. However, in some instances, it may be
desirable to actually deposit an intermediate layer above the
surface 21. In this instance, an actual intermediate layer 23 is
formed above the surface 21 and in which the termination sites are
actually present on this layer 23. This is illustrated in FIG. 10.
Again, this layer can be deposited by a plasma process, including
ALD. Then, the ALD process sequence, commencing with the deposition
of ML.sub.x can commence.
An intermediate layer may be required in some instances when the
substrate cannot be made reactive with either of the ALD molecular
precursors by a simple attachment or exchange of surface species.
The ultra thin intermediate layer 23 is deposited as part of the
pretreatment process. The intermediate layer 23 provides a new
surface that is reactive to one or both precursors. The layer 23 is
formed having a thickness which is kept minimal, but sufficient for
activation. The intermediate layer 23 may be conductive,
semiconductive or insulating (dielectric). Typically, it will match
the electrical properties of either the substrate 20 or the
overlying film being grown. For example, layer 23 is needed as a
transition layer when W or WN.sub.x films are deposited on
SiO.sub.2. In this instance, Al.sub.2 O.sub.3 (which is an
insulator) or TiN, Ti, Ta or Ta.sub.x N (which are conductors) can
be used for the intermediate layer 23.
It is to be noted further, that the intermediate layer 23 can be
deposited by ALD for the pretreatment of the surface. Additionally,
the surface 21 of the substrate 20 can be pretreated first by the
first method described above to prepare the surface 21 for the
deposition of the intermediate layer 23. Although this does require
additional process, it may be desirable in some instances.
It is appreciated that the pretreatment of surface 21 is achieved
by a plasma process in the above description, including the use of
ALD. However, other techniques can be used instead of a plasma
process to pretreat the surface 21. Thus, the surface 21 can be
treated, even the intermediate layer 23 grown, by other techniques.
Furthermore, a leaching process an be utilized. Since some surfaces
are quite inert, a process other than reactive exchange or
attachment may be desirable. For example, hydrocarbon and
fluorocarbon polymers are utilized for low-k dielectrics. Adhesion
of films, for sealing (insulating) or for forming a barrier
(metals, metal nitrides), is difficult to achieve. In these
instances, leaching hydrogen or fluorine from the top layer of the
polymer can activate the surface for ALD.
Thus, a number of techniques are available for pretreating a
surface of a substrate so that the surface is more active for ALD.
The present invention can be implemented in practice by a number of
chemistries and chemical reactions. A number of examples are
provided below with relevant equations. It is to be understood that
the examples listed below are provided as examples and in no way
limit the invention to just these examples.
EXAMPLE 1
ALD deposition of Al.sub.2 O.sub.3 on silicon. A silicon substrate
is first activated (pretreated) by forming thin layers of silicon
oxide (SiO.sub.2) or silicon oxinitride, in which OH and/or
NH.sub.x groups form the terminations. The process involves O.sub.2
/H.sub.2 /H.sub.2 O/NH.sub.3 remote plasma that includes different
ratios of the constituents to form the terminations prior to the
introduction of the first precursor to grow the Al.sub.2 O.sub.3
thin film layer on silicon.
Si--H--OH.+H.+NH.sub.x..fwdarw.Si--OH+Si--NH.sub.x (where "."
defines a radical)
Si--OH+Al(CH.sub.3).sub.3.fwdarw.Si--O--Al(CH.sub.3).sub.2
+CH.sub.4 Si--NH.sub.x +Al(CH.sub.3).sub.3.fwdarw.Si--NH.sub.x-1
--Al(CH.sub.3).sub.2 +CH.sub.4
EXAMPLE 2
ALD deposition of AL.sub.2 O.sub.3 on silicon. The silicon
substrate is activated by forming thin layers of SiO.sub.2 that is
hydroxilated by exposing HF cleaned (H terminated) silicon to a
pulse of H.sub.2 O at temperatures below 430.degree. C. This
process results in a self-saturated layer of SiO.sub.2 that is
approximately 5 angstroms thick. Si--H+H.sub.2
O.fwdarw.Si--O--Si--OH+H.sub.2
Si--OH+Al(CH.sub.3).sub.3.fwdarw.Si--O--Al(CH.sub.3).sub.2
+CH.sub.4
EXAMPLE 3 ALD deposition of Al.sub.2 O.sub.3 on WN.sub.x. NH.sub.3
/H.sub.2 /N.sub.2 plasma is used to leach fluorine from the top
layers of the WN.sub.x film and terminate the surface with NH.sub.x
species. These species are reacted with trimethyl aluminum (TMA) to
initiate deposition of Al.sub.2 O.sub.3 on WN.sub.x. W.sub.x
N+H.+NH.sub.x..fwdarw.W--NH.sub.x W--NH.sub.x
+Al(CH.sub.3).sub.3.fwdarw.W--NH.sub.x-1 --Al(CH.sub.3).sub.2
+CH.sub.4
EXAMPLE 4
ALD deposition of Al.sub.2 O.sub.3 on TiN. NH.sub.3 /H.sub.2
/N.sub.2 plasma is used to terminate the surface with NH.sub.x
species. These species are reacted with TMA to initiate Al.sub.2
O.sub.3 ALD. TiN+H.+NH.sub.x..fwdarw.Ti--NH.sub.x TiNH.sub.x
+Al(CH.sub.3).sub.3.fwdarw.TiNH.sub.x-1 --Al(CH.sub.3).sub.2
+CH.sub.4
EXAMPLE 5
ALD deposition of Al.sub.2 O.sub.3 on Ti. NH.sub.3 /H.sub.2
/N.sub.2 plasma is used to nitridize the surface and terminate the
surface with NH.sub.x species. Maintain conditions to avoid
extensive nitridization into the Ti film. The NH.sub.x species are
reacted with TMA to initiate Al.sub.2 O.sub.3 ALD.
Ti+NH.sub.x.+H..fwdarw.TiNH.sub.x TiNH.sub.x
+Al(CH.sub.3).sub.3.fwdarw.TiNH.sub.x -1 --Al(CH.sub.3).sub.2
+CH.sub.4
EXAMPLE 6
ALD deposition of Al.sub.2 O.sub.3 on W. NH.sub.3 /H.sub.2 /N.sub.2
plasma is used to nitridize the surface and terminate the surface
with NH.sub.x species. Maintain conditions to avoid extensive
nitridization into the W film. The NH.sub.x species are reacted
with TMA to initiate Al.sub.2 O.sub.3 ALD.
W+NH.sub.x.+H..fwdarw.WNH.sub.x W--NH.sub.x
+Al(CH.sub.3).sub.3.fwdarw.W--NH.sub.x-1 --Al(CH.sub.3).sub.2
+CH.sub.4
EXAMPLE 7
ALD deposition of Al.sub.2 O.sub.3 on Ta. NH.sub.3 /H.sub.2
/N.sub.2 plasma is used to nitridize the surface and terminate the
surface with NH.sub.x species. Maintain conditions to avoid
extensive nitridization into the Ta film. The NH.sub.x species are
reacted with TMA to initiate Al.sub.2 O.sub.3 ALD.
Ta+NH.sub.x.+H..fwdarw.TaNH.sub.x TaNH.sub.x
+Al(CH.sub.3).sub.3.fwdarw.TaNH.sub.x-1 --Al(CH.sub.3).sub.2
+CH.sub.4
EXAMPLE 8
ALD deposition of Al.sub.2 O.sub.3 on Ta.sub.x N. NH.sub.3 /H.sub.2
/N.sub.2 plasma is used to terminate the surface with NH.sub.x
species. The NH.sub.x species are reacted with TMA to initiate
Al.sub.2 O.sub.3 ALD. Ta.sub.x N+NH.sub.x.+H..fwdarw.TaNH.sub.x
TaNH.sub.x +Al(CH.sub.3).sub.3.fwdarw.TaNH.sub.x-
--Al(CH.sub.3).sub.2 +CH.sub.4
EXAMPLE 9
ALD deposition of Ta.sub.2 O.sub.5 on Al.sub.2 O.sub.3. The process
involves O.sub.2 /H.sub.2 /H.sub.2 O remote plasma that includes
different ratios of the constituents. This plasma is used to
terminate the surface with OH species that are reactive with
TaCl.sub.5. Al.sub.2 O.sub.3 +OH.+O.+H..fwdarw.Al.sub.2 O.sub.3
--OH Al.sub.2 O.sub.3 -OH+TaCl.sub.5.fwdarw.Al.sub.2 O.sub.3
--O--TaCl.sub.4 +HCl
EQUATION 10
ALD deposition of Al.sub.2 O.sub.3 on Ta.sub.2 O.sub.5. The process
involves O.sub.2 /H.sub.2 /H.sub.2 O remote plasma that includes
different ratios of the constituents. This plasma is used to
terminate the surface with OH species that are reactive with
TaCl.sub.5. Ta.sub.2 O.sub.5 +O.+H.+OH..fwdarw.Ta.sub.2 O.sub.5
--OH Ta.sub.2 O.sub.5 --OH+Al(CH.sub.3).sub.3.fwdarw.Ta.sub.2
O.sub.5 --O--Al(CH.sub.3).sub.2 +CH.sub.4
EXAMPLE 11
ALD deposition of TiO.sub.x on Al.sub.2 O.sub.3. The process
involves O.sub.2 /H.sub.2 /H.sub.2 O remote plasma that includes
different ratios of the constituents. This plasma is used to
terminate the surface with OH species that are reactive with TMA.
Al.sub.2 O.sub.3 +O.+H.+OH..fwdarw.Al.sub.2 O.sub.3 --OH Al.sub.2
O.sub.3 --OH+TiCl.sub.4.fwdarw.Al.sub.2 O.sub.3 --O--TiCl.sub.3
+HCl
EXAMPLE 12
ALD deposition of Al.sub.2 O.sub.3 on TiO.sub.x. The process
involves O.sub.2 /H.sub.2 /H.sub.2 O remote plasma that includes
different ratios of the constituents. This plasma is used to
terminate the surface with OH species that are reactive with
TiCl.sub.4. TiO.sub.2 +O.+H.+OH..fwdarw.TiO.sub.2 --OH TiO.sub.2
--OH+Al(CH.sub.3).sub.3.fwdarw.TiO.sub.2 --O--Al(CH.sub.3).sub.2
+CH.sub.4
EXAMPLE 13
ALD deposition of TiO.sub.x on TiN. NH.sub.3 /H.sub.2 /N.sub.2
plasma is used to terminate the surface with NH.sub.x species. The
NH.sub.x species are reacted with TiCl.sub.4 to initiate TiO.sub.x
ALD. TiN+H.+NH.sub.x..fwdarw.Ti--NH.sub.x Ti--NH.sub.x
+TiCl.sub.4.fwdarw.TiNH.sub.x-1 --TiCl.sub.3 +HCl
EXAMPLE 14
ALD deposition of W on TiN. NH.sub.3 /H.sub.2 /N.sub.2 plasma is
used to terminate the surface with NH.sub.x species. The NH.sub.x
species are reacted with TiCl.sub.4 to initiate TiN ALD.
TiN+H.+NH.sub.x..fwdarw.Ti--NH.sub.x Ti--NH.sub.x
+WF.sub.6.fwdarw.TiNH.sub.x-1 --WF.sub.5 +HF
EXAMPLE 15
ALD deposition of WN.sub.x on TiN. NH.sub.3 /H.sub.2 /N.sub.2
plasma is used to terminate the surface with NH.sub.x species. The
NH.sub.x species are reacted with TiCl.sub.4 to initiate WN.sub.x
ALD. TiN+H.+NH.sub.x..fwdarw.Ti--NH.sub.x Ti--NH.sub.x
+WF.sub.6.fwdarw.TiNH.sub.x-1 --WF.sub.5 +HF
EXAMPLE 16
ALD deposition of WN.sub.x on SiO.sub.2. O.sub.2 /H.sub.2 /H.sub.2
O remote plasma that includes different ratios of the constituents
is used to terminate the surface with OH species that are reactive
with TiCl.sub.4. The TiCl.sub.4 species is used to grow an
intermediate layer of Ti or TiN. The final layer is terminated with
NH.sub.x species (from the TiN ALD) which reacts with WF.sub.6 to
initiate the WN.sub.x ALD process. SiO.sub.2
+H.+O+OH..fwdarw.Si--OH Si--OH+TiCl.sub.4.fwdarw.SiO--TiCl.sub.3
+HCl SiO--TiCl.sub.3 +NH.sub.3.fwdarw.SiO--TiN--NH.sub.x +HCl
SiO--TiN--NH.sub.x +WF.sub.6.fwdarw.SiO--TiN--NH.sub.x-1 WF.sub.5
+HF
EXAMPLE 17
ALD deposition of W on SiO.sub.2. O.sub.2 /H.sub.2 /H.sub.2 O
remote plasma that includes different ratios of the constituents is
used to terminate the surface with OH species that are reactive
with TiCl.sub.4. The TiCl.sub.4 species is used to grow an
intermediate layer of Ti or TiN. The final layer is terminated with
NH.sub.x species (from the TiN ALD) which reacts with WF.sub.6 to
initiate the W ALD process. SiO.sub.2 +H.+O.+OH..fwdarw.Si--OH
Si--OH+TiCl.sub.4.fwdarw.SiO--TiCl.sub.3 +HCl SiO--TiCl.sub.3
+NH.sub.3.fwdarw.SiO--TiN--NH.sub.x +HCl SiO--TiN--NH.sub.x
+WF.sub.6.fwdarw.SiO--TiN--NH.sub.x-1 WF.sub.5 +HF
Alternatively, TaCl.sub.5 can be used for growing an intermediate
Ta.sub.x N layer.
EXAMPLE 18
ALD deposition of WN.sub.x on hydrocarbon polymer (low-k dielectric
layer). NF.sub.3 remote plasma generates fluorine atoms that leach
out hydrogen from the hydrocarbon. The leached surface is reacted
with TiCl.sub.4 and followed by TiN or Ti/TiN ALD of a thin
intermediate layer. The NH.sub.x terminated surface that is
prepared during the TiN ALD is reacted with WF.sub.6 to initiate
WN.sub.x ALD. C.sub.n H.sub.m +F..fwdarw.C.sub.p H.sub.q C. C.sub.p
H.sub.q C.+TiCl.sub.4.fwdarw.C.sub.p H.sub.q-1 CTiCl.sub.3 +HCl
C.sub.p H.sub.q-1 CTiCl.sub.3 +NH.sub.3.fwdarw.C.sub.p H.sub.q-1
CTiN--NH.sub.x +HCl C.sub.p H.sub.q-1 CTiN--NH.sub.x
+WF.sub.6.fwdarw.C.sub.p H.sub.q-1 CTiN--N.sub.x-1 --WF.sub.5
+HF
EXAMPLE 19
ALD deposition of WN.sub.x on perfluorocarbon polymer (low-k
dielectric layer). H.sub.2 /NH.sub.3 remote plasma generates H
atoms and NH.sub.x radicals that leach out fluorine from the
hydrocarbon. The leached surface is reacted with TiCl.sub.4 and
followed by TiN or Ti/TiN ALD of a thin intermediate layer. The
NH.sub.x terminated surface that is prepared during the TiN ALD is
reacted with WF.sub.6 to initiate WN.sub.x ALD. C.sub.m F.sub.n
+H.+NH.sub.x..fwdarw.C.sub.p F.sub.q C.+HF C.sub.p F.sub.q
C.+TiCl.sub.4.fwdarw.C.sub.p F.sub.q C--TiN--NH.sub.x C.sub.p
F.sub.q C--TiN--NH.sub.x +WF.sub.6.fwdarw.C.sub.p F.sub.q
C--TiNH.sub.x-1 --NWF.sub.5 +HF
EXAMPLE 20
ALD deposition of oxide on another oxide. The surface of the first
oxide is activated by O.sub.2 /H.sub.2 /H.sub.2 O remote plasma
that includes different ratios of the constituents. This process is
used to terminate the surface with OH species that are reactive
with a metal precursor for the next oxide layer. M1O.sub.x
+O.+H.+OH..fwdarw.M1O.sub.x --OH M1O.sub.x
--OH+M2L.sub.y.fwdarw.M1O.sub.x --O--M2L.sub.y-1 +HL
EXAMPLE 21
ALD deposition of oxide on metal, semiconductor or metal nitride.
NH.sub.3 /H.sub.2 /N.sub.2 plasma is used to terminate the surface
with NH.sub.x species that are reactive with a metal precursor for
initiating ALD. M1+H.+NH.sub.x..fwdarw.M1.fwdarw.NH.sub.x
M1NH.sub.x +M2L.sub.y.fwdarw.M1NH.sub.x-1 M2L.sub.y-1 +HL
EXAMPLE 22
ALD deposition of metal, semiconductor or conductive metalnitride
on oxide. NH.sub.3 /H.sub.2 /N.sub.2 plasma is used to terminate
the surface with NH.sub.x species or O.sub.2 /H.sub.2 /H.sub.2 O
plasma generated radicals are used to terminate the surface with OH
species. The species are reactive with a metal precursor for
initiating ALD. M1O.sub.x +O.+H.+OH..fwdarw.M1O.sub.x --OH
M1O.sub.x --OH+M2L.sub.y.fwdarw.M1O.sub.x --O--M2L.sub.y-1 +HL
Again, it is appreciated that the above are described as examples
only and that many other ALD reactions and pretreatment procedures
are available.
Referring to FIG. 11, an apparatus for practicing the present
invention is shown. An ALD reactor apparatus 30 is shown as one
embodiment. It is appreciated that a variety of other devices and
equipment can be utilized to practice the invention. Reactor 30
includes a processing chamber 31 for housing a wafer 32. The wafer
32 comprises the substrate 20 described in the earlier Figures.
Typically, the wafer 32 resides atop a support (or chuck) 33. A
heater 34 is also coupled to the chuck to heat the chuck 33 and the
wafer 32 for plasma deposition. The processing gases are introduced
into the chamber 31 through a gas distributor 35 located at one end
of the chamber 31. A vacuum pump 36 and a throttling valve 37 are
located at the opposite end to draw and regulate the gas flow
across the wafer surface.
A mixing manifold 38 is used to mix the various processing gases
and the mixed gases are directed to a plasma forming zone 39 for
forming the plasma. A variety of CVD techniques for combining gases
and forming plasma can be utilized, including adapting techniques
known in the art. The remotely formed plasma is then fed into gas
distributor 35 and then into the chamber 31.
The mixing manifold 38 has two inlets for the introduction of gases
and chemicals. A carrier gas is introduced and the flow split at
the mixing manifold 38. The carrier gas is typically an inert gas,
such as nitrogen. The mixing manifold 38 also has two inlets for
the chemicals. In the example diagram of FIG. 11, chemical A and
chemical B are shown combined with the carrier gas. Chemistry A
pertains to the first precursor and chemistry B pertains to the
second precursor for performing ALD for the two precursor process
described above. Chemical selection manifold 40 and 41, comprised
of a number of regulated valves, provide for the selecting of
chemicals that can be used as precursors A and B, respectively.
Inlet valves 42 and 43 respectively regulate the introduction of
the precursor chemistries A and B into the mixing manifold 38.
The operation of the reactor for performing ALD is as follows. Once
the wafer is resident within the processing chamber 31, the chamber
environment is brought up to meet desired parameters. For example,
raising the temperature of the wafer in order to perform ALD. The
flow of carrier gas is turned on so that there is a constant
regulated flow of the carrier gas as the gas is drawn by the vacuum
created by the pump 36. When ALD is to be performed, valve 42 is
opened to allow the first precursor to be introduced into the
carrier gas flow. After a preselected time, valve 42 is closed and
the carrier gas purges any remaining reactive species. Then, valve
43 is opened to introduce the second precursor into the carrier gas
flow. Again after another preselected time, the valve 43 is closed
and the carrier gas purges the reactive species form the chambers
of the reactor. The two chemicals A and B are alternately
introduced into the carrier flow stream to perform the ALD cycle to
deposit a film layer.
When the pretreatment of the surface is to be performed by plasma,
the pretreating species can be introduced into the mixing manifold
through either or both of the chemical selection routes through
selection manifold(s) 40, 41 to mix with the carrier gas. Again,
the pretreatment is performed prior to the initial introduction of
the first ALD precursor used to deposit the film. Accordingly, the
introduction of the pretreatment chemistry can be achieved from
adapting designs of a standard ALD reactor.
Thus, an apparatus and method to achieve continuous interface and
ultrathin film during atomic layer deposition is described. The
present invention allows an ALD process to start continuously
without nucleation or incubation and allows ultrathin film layers
of 50 angstroms or less in thickness to be deposited having
continuous uniformity and/or conformity.
* * * * *